Transmission Overheats in All Ranges for Chevrolet Chevrolet C-Series Medium Duty Truck B7 1999

The cooler lines are restricted.

1. Remove the restrictions.
2. Clean or replace the lines as necessary. Refer to Transmission Oil Cooler Line Replacement .

The torque converter has broken parts.

Repair or replace the converter assembly.

The oil is aerated.

Check the following:

Internal leakage is slowing the oil cooling flow.

Overhaul the transmission.